Is my brain making me buy things I don't need?

To test the subjects' shopping behaviors, the study group gave 26 subjects $40 in cash each and stuck them in an MRI machine one at a time. Inside the machine, the researchers showed each subject a series of product images followed by an image showing the price of the product. If the subject chose to buy the product, its price was deducted from the $40 and it was shipped to them. Whatever was left of the $40 after the MRI shopping session, the subject got to keep.

The results were so standardized that the researchers were a bit stunned. When a product image flashed, the area of the brain called the nucleus accumbens lit up if the subject liked what he or she saw. That means there was increased neural firing in that area of brain, which is the "pleasure center" of the brain with lots of dopamine receptors that make for feelings of happiness and excitement in anticipation of a nice event. This is the first result: The nucleus accumbens experiences an increase in activity -- an anticipation of pleasure -- when consumers like what they see.

The second image, the one showing the price, triggered a different part of the brain, and it's this brain activity that let researchers know if the subject would buy the product before the subject was even aware of having made a decision. When the price appeared, the insula either lit up, or it didn't. The insula is sort of the opposite of the pleasure center. Its neurons start firing when you realize you're about to slam your finger in a door, for instance. When the insula lit up, the subject ultimately decided not to buy the product. When the insula did not light up, and the nucleus accumbens had been activated on viewing the product, the subject eventually decided to buy it. This is the second result of the­ study: When neurons start firing in the insula, the decision not to make the purchase has been made on an unconscious level, based on the anticipation of pain. The conscious decision comes a bit later, and it always follows the unconscious decision made by the insula.

The problem for some subjects was that insula almost never lit up, and they went home with none of the $40 cash they'd been given at the start of the experiment. These, most likely, would be the people with the jaw-dropping credit card bills. Or 12 pairs of black pumps. The researchers plan to perform a similar study involving people with compulsive-shopping habits to see how their brains compare to the general population.

For more information on the brain's "shopping center" and related topics, check out the links below.